Measuring concentrations of various components (e.g., chemical elements or compounds) in gas samples often requires complex and expensive equipment. For example, oxygen concentration is typically measured using a polarographic electrode, fuel cell, and paramagnetic analyzer. Carbon dioxide concentration is measured using an infrared analyzer, molecular correlation spectrography, and photoacoustic spectrography. Other conventional techniques include mass spectrometry, Raman spectroscopy, refractometry, gas chromatography, non-dispersive infrared analysis, differential absorption light detection and ranging analysis, chemiluminescence analysis, tunable diode laser absorption spectroscopy, and the like. These techniques and corresponding devices, while precise and accurate, are costly, bulky, and often fragile. As a result of these complexities and costs, gas concentration analysis is not as widely adopted as desired, especially in the field (away from laboratories), tight spaces, and the like.
At the same time, gas concentration analysis is important from safety, process control, and other standpoints. For example, when a fuel tank is flushed with carbon dioxide (CO2), it is important to determine or at least roughly estimate the concentration of carbon dioxide in the tank before a person can safely enter the tank without a breathing apparatus. In another example, the concentration of ethyl alcohol (or another solvent) in a smoothing container used for three-dimensional (3-D) printing needs to be maintained within a range. As 3-D printing gains popularity and becomes more affordable, this solvent concentration control becomes problematic. In both examples presented above, the expected components are known, and only concentrations of these components are needed.
What is needed are methods and systems for measuring concentration of known components in gas samples.